Support cradle for rolled coils and other cylindrical objects

ABSTRACT

A cradle unit for supporting metal coils, and other cylindrical objects, consists of two, parallel and separate saddles made of polyurethane or other material having a hardness range of between 50 Shore A and 90 Shore D, which saddles are connected together via a pair of parallel steel angle-brackets that provide inherent structural integrity to the cradle unit itself, while still allowing the unit to conform to the shape or level of the underlying support structure. The single cradle unit may be as a mobile support-device, or may be bolted or otherwise attached to a surface for a specific location of the stored product. The cradle unit is generally concave-shaped and has a first main or central lower concave curvature of a first radius, and a middle or secondary transitional curvature that connects the first main lower curvature to an upper, tertiary concave curvature of a second radius greater than the first radius, so that coils or rolls of different diameter may be safely and firmly supported. In a modification, a pair of rails are provided for fixedly mounting and supporting a plurality of support cradles, where each support cradle is held in place by the rails via metal pins protruding or projecting from the bottom surface of the support cradle that are received in openings formed the rails, whereby no lateral or longitudinal movement or sliding of the support cradles is possible.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional application of application Ser. No. 11/428,623, which is a continuation-in-part of application Ser. No. 11/208,953, filed on Aug. 22, 2005, now U.S. Pat. No. 7,448,505.

BACKGROUND OF THE INVENTION

The present invention is directed to a cradle unit, or supporting member, for supporting and storing coils, such as wound rolls or coils of long lengths of thin flat material made of steel, other metal, paper, or the like, which are processed, handled, stored and transported with the longitudinal axis of the coil oriented in the horizontal direction. When stored in their semi-finished, in-process stage between operations, in their finished state awaiting shipment, or during actual shipment and final storage during actual use, these coils are placed in designated staging areas by supporting them on the floor, since allowing these coils to rest directly on the floor or other flat surface would produce highly-stressed loading at the tangential contact points. Even though these coils may be made of metal, they are relatively soft or pliable, and susceptible to damage from scratching, denting or surface-marking when they impinge upon debris on the floor or on another hard storage surface.

Many locations where coils are stored are on floors that are not flat, tending to misshape or deform the coil over time. Coils may also be damaged from flattening or denting when set down during handling operations, or from excessive pressure or weight while sitting in storage due to single-point tangential and high surface-loading. This situation is exacerbated when coils are stacked during storage, which is common in the metals industries. Therefore, significant expense is incurred from the lost metal and rework of the damaged coils. Additionally, stacked coils, when stored on flat floors, represent a safety hazard from roll out of the bottom tier of the stack. This situation is hazardous to personnel, the facilities and the coils that would be affected by such a collapse of the stack.

There have been used a number of various techniques in an attempt to address the above-mentioned problems. Some of these techniques include: setting coils on rubber or fabric belting; using rubber or polyurethane pads with slight indentations to cradle the coil; using “V”-shaped blocks made of polyurethane, plastic, wood or metal; and unitized skids of plastic, wood or metal, or other similarly constructed devices to contain or protect the coils.

Polyurethane, rubber and plastic coil-support devices possess the ability to cushion the coil during set-down. These devices are typically molded or formed into a single unit, and do not provide suitable strength or structural integrity to support stacks of coils without the use of additional, independent, and separate support structures. Wood supports are not resilient or durable, while metal fabricated supports do not cushion and offer a surface that has is basically the same as a bare floor. Unitized fabrications of wood, plastic or steel are expensive to build, do not offer the durability and protection of a resilient support, and do not conform or adapt to uneven floor conditions.

An example of a prior-art support is disclosed in U.S. Pat. No. 4,503,978—Smit, et al., and discloses a support for rolled coils made of polyethylene. The supports of this patent do not generally provide adequate structural support, and, therefore, are typically supported by U-shaped steel channels bolted to the floor, or other supporting surfaces, and are generally not conformable to a support under-structure.

SUMMARY OF THE INVENTION

It is, therefore, the primary objective of the present invention to provide a support cradle for coils, rolls, or other cylindrical objects that provides its own inherent structural integrity for solely supporting a coil thereon, while also conforming to the under-structure upon which it is rests, which support cradle may be used to support coils or rolls of different diameter.

It is, also, the primary objective of the present invention to provide such a support cradle that provides its own inherent structural integrity for supporting a coil thereon, while also conforming to the under-structure upon which it is secured, which support may also be connected to other like-cradles for forming a multi-unit cradle-support for supporting a series of coils thereon, while still maintaining its conforming characteristics for preventing damage to the coils supported thereon, and for safely stacking of rows of coils thereabove.

In it, also, the primary objective of the present invention to provide a pair of rails for fixedly mounting and supporting a plurality of support cradles, where each support cradle is held in place by the rails via metal pins protruding or projecting from the bottom surface of the support cradle that are received in openings formed the rails, while the rails themselves are affixed to the floor, whereby no lateral or longitudinal movement or sliding of the support cradles is possible.

In accordance with the invention, the cradle unit for supporting metal coils, and other cylindrical objects, consists of two parallel and separate cradle-sections or saddles made of polyurethane, or other material, having a hardness range of between 50 Shore A and 90 Shore D, which cradle-sections are joined or connected together via a pair of parallel steel angle-brackets that provide inherent structural integrity to the cradle unit itself, while still allowing the saddles to conform to the shape or level of the underlying support structure, whereby a plurality of cradle units may be used for supporting coils in a tiered stack. The single cradle unit may be used as a mobile support-device, or may be bolted or otherwise attached to a surface for a specific location of the stored product. The cradle unit of the invention may, also, be attached to the bed of a transportation vehicle, such as a truck trailer or rail car, in order to provide secure, protective storage and location of the items. In this case, the nature of the resilient or soft material from which the cradle unit is made provides shock-absorption qualities for the transported coil.

The cradle unit generally defines a concave-shaped upper surface, and has a first main or central lower concave curvature of a first radius, a pair of middle or secondary transitional curvature-sections that connect the first main lower curvature to a pair of upper, tertiary concave curvature-sections of a second radius greater than the first radius, so that coils or rolls of different diameter may be safely and firmly accommodated.

In a modification of the invention, a multiple-unit version is provided where a series of cradle units of the invention are connected together to form one elongated integral support structural unit. This modification is a unitized rack that forms a row-storage arrangement where the stored coils or objects are stored randomly along the length of the rack, for securing and protecting the stored coils or objects, with the coils arranged lengthwise along the length of the rack.

In another modification, each cradle unit is provided with outwardly-projecting oil-receiving pans or reservoirs for collecting oil or other liquid lubricant seeping or draining out from the ends of the coil supported thereby. These pans provide for the containment of the fluid to prevent contamination of the surrounding environment, and provide for safe, easy recovery and disposal of the liquid.

In yet another modification, a plurality of support cradles are loosely mounted in place to a pair of rails which, in turn, is affixed to a floor in order to prevent sliding of the support cradles while allowing for flexing of the support cradles under full-load conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood with reference to the accompanying drawings, wherein:

FIG. 1 is an isometric view of the cradle unit for supporting a coil, roll, or other cylindrical object in accordance with the invention;

FIG. 2 is a top view thereof.

FIG. 3 is a side, elevational view thereof,

FIG. 4 is an end view thereof,

FIG. 5 is an isometric view showing a series of cradle units of FIG. 1 being used to support a tiered stack of coils or rolls;

FIG. 6 is an isometric view similar to FIG. 5 showing the force vectors acting on the coils or rolls and on the series of cradle units supporting the stack of coils or rolls;

FIG. 7 is an isometric view of a modification in which a series of cradle units of FIG. 1 are provided in one unitary structure for forming a rack for supporting a series of coils, rolls, or other cylindrical objects in a row;

FIG. 8 is an end view thereof,

FIG. 9 is a side elevational view thereof,

FIG. 10 is an isometric view showing a series of cradle racks of FIG. 7 being used to support a plurality of stacked rows of coils or rolls;

FIG. 11 is an isometric view of another modification of the cradle unit of FIG. 1 with the addition of a pair of end-pans serving as reservoirs for collecting lubricant draining from coils or rolls supported or stacked thereon;

FIG. 12 is a side elevational view thereof,

FIG. 13 is a top view thereof,

FIG. 14 is an end view thereof,

FIG. 15 is a side view of yet another modification of the cradle unit where each the cradle unit is provided with protruding metal pins for reception in openings of a pair of rails affixed to a floor, or the like, by which the cradle unit is retained in place and prevented from sliding movement;

FIG. 16 is a top view thereof,

FIG. 17 is an end view thereof,

FIG. 18 is a top plan view of a rail fixable to a floor or other understructure to a pair of which rails a cradle unit of FIG. 15 is secured;

FIG. 19 is a top plan view of a pair of rails of FIG. 18 affixed to a floor or other understructure and shown supporting and securing a plurality of cradle units of FIG. 15 in a spaced apart manner via the protruding metal pins of the cradle units received in openings of the rails; and

FIG. 20 is a side elevational view of FIG. 19.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings in greater detail, and to FIGS. 1-6 for now, there is shown a cradle unit 10 of the invention for supporting a coil, roll, or other large cylindrical object. The cradle unit 10 consists of a pair of parallel-arranged, identical end-cradle sections or saddles 12, 14 preferably made of polyurethane, in the hardness range of between 50 Shore A and 90 Shore D. The length of each end-cradle section or saddle 12, 14 depends upon the size or sizes of the coils or rolls to be supported. In one example, each end-cradle section is thirty three inches in length and three inches in width. Each end-cradle section or saddle 12, 14 defines an upwardly-facing concave supporting surface 16, 18 which consists of a first lower or main portion 16′, 18′, respectively, having a first radius R1, and second upper or tertiary end portions 16″, 18″ each having a second radius R2 that is greater than the radius R1. Connecting the surface-portion 16′ or 18′ with the portions 16″ or 18″ are transitional curvature-portions or regions 20, 22, respectively. The values of R1 and R2 will vary depending upon the size of coils or rolls to be supported. The value R1 corresponds to the radius of the minimal coil or roll to be supported by the cradle 10, while the value R2 corresponds to the radius of the maximal coil or roll to be supported by the cradle 10. In the example given above, the first radius R1 is twenty inches, while the second radius R2 is thirty six inches, with the height of each end-cradle section or saddle increasing from a minimum of one inch at the midpoint or center to a maximum of five inches at the extremity or end 24, 26.

With regard to the transitional regions 20, 22, it is noted that the first lower or main portion 16′, 18′ and the second upper or tertiary end portions 16″, 18″ not only have different radii R1 and R2, but, of course, also have different points of centers pt1 and pt2, respectively. The shape or curvature of each transition region 20, 22 is formed by generating a number of circles of different radii and from a varying center position pt[i] between the center points pt1 and pt2 in a linear relationship. Using the equation: pt[i]=pt1+(pt2−pt1)/(r2−r1)*abs(r1−r[i]), where pt[i] is a center point of a transitional circle and r[i] is the radius of the transitional circle, connecting the tangents of these generated circles form the curve of each transition region 20, 22.

The cradle unit 10 also includes a pair of parallel-arranged steel angle-brackets 30, 32 which provide the inherent structural integrity to the unit. Each angle-bracket connects corresponding ends of the two end-cradle sections 12,14, as seen in FIG. 1. Each angle-bracket 30, 32 consists of a horizontal section 34 and a vertical section 36, with a respective end of a cradle unit being nestled therein. The right-angle brackets are bonded to the ends of the end-cradle sections by conventional bonding techniques, whereby a flexible and adaptable rectilinear-shaped structure is formed. In the above-mentioned example, the length of each angle bracket may be typically thirty-six inches, with the width of each of the horizontal and vertical sections typically being three inches, and typically made of 3/16″ steel. Each horizontal section 34 may be provided with a pair of holes 46 for passing therethrough bolts for securing the cradle unit 10 to a floor or other under-structure.

Referring to FIGS. 5 and 6, it may be seen how a series of cradle units 10 may be used to support a tiered vertical stack of rows of coils or rolls 40. The force vector diagram depicts coils C1 through C8 stacked on the coil cradle units 10 of the invention. The loads are calculated as if the stack continues on to the left of the diagram. Each coil shown has been assumed to be of a 72″ O.D. and a weight W. Because of the stacking, the downward force W splits into the two vector forces W_(L) and W_(R). For purposes of clarity, only coil C2 has been shown with the forces labeled. On the middle row, the forces acting on coil C4 are its weight W plus W_(R) from coil C1 and W_(L) from coil C2. The resultant force, 2 W, is drawn using vector addition. The forces acting on coil C5 are its weight W plus W_(R) from coil C2. The resultant force is drawn using vector addition. On the bottom row, the forces acting on coil C6 are its weight W plus 2·W_(R) from coil C3 and 2·W_(L) from coil C4. The resultant force, 3·W, is drawn using vector addition. The forces acting on coil C7 are its weight W plus 2·W_(R) from coil C4 and W_(L) from coil C5. The resultant force is drawn using vector addition. The forces acting on coil C8 are its weight W plus 2·W_(R) from coil. The resultant force is drawn using vector addition. On the bottom row, lines are drawn from the center of the coils to the edges of the ends 24, 26 of the cradle units. If the resultant force vectors remain in between these lines, the stack will be stable, assuming that the coils in the stack are frictionless and not considering inertia. In actual use, the stack could be stable even if this limit were somewhat exceeded. Because of the provision of two separate upper curved sections of different radii R1 and R2 for each cradle unit, multiple layers of coils of different diameter may be more safely stacked, as shown in FIGS. 5 and 6.

Referring now to FIGS. 7-10, there is a shown a modification in which a series of cradle units 10 are provided to form a rack 50 of cradles for supporting a plurality of individual coils thereon end-to-end to form a ladder-like structure. The rack 50 consists of a plurality of cradle elements 52 similar to the end-cradle sections 12, 14 of the cradle unit 10, which cradle sections 52 are interconnected together by a pair elongated steel angle-brackets 54, 56 similar to the angle-brackets 30, 32 of the cradle unit 10 of FIG. 1. The spacing between the cradle elements 52 is generally less than the spacing between the end-cradle sections or saddles 12, 14 of the cradle unit 10. Whereas the spacing between the cradle sections 12, 14 in one example cited above is thirty inches, the spacing between adjacent cradle elements 52 is 15¼ inches, so that, not only variously-sized rolls or coils of different diameters may be supported and stored on the rack 50, but also coils or rolls of different lengths may be supported thereby. In addition, owing to the series arrangement of cradle sections 52, the placing of a coil or roll on the rack 50 may be achieved at any portion along the length thereof thereby allowing facility of placement and storage. A plurality of racks 50 may be employed in parallel formation, as shown in FIG. 10, in order to allow for support and storage of multiple, stacked rows of coils or rolls 40. The spacing between racks 50 is dependent upon the size of the coils or rolls 40 to be supported. Each individual rack 50 is bolted to the floor or under-structure by bolts passing through the angle brackets, in the same manner described above with reference to the cradle unit 10. In addition, oil pans similar to oil pans described hereinbelow with reference to FIGS. 11-14, may also be used for collecting oil, or other fluid. It is noted that the individual rolls or coils are supported end-to-end, with their longitudinal axes being parallel to the length of the rack, whereby the rack 50 supports them in the manner that has hithertofore only been done using a coil pad. Thus, the rack 50 serves the dual function of acting as cradle supports and as a coil pad.

Referring now to FIGS. 11-14, there is shown another modification 60 of the cradle unit 10 in which a pair of oil-collecting pans or reservoirs 62, 64 are provided at the ends of the cradle unit in order to collect oil or other lubricant or fluid seeping or draining out from the ends of the coil supported thereby. These pans provide for the containment of the fluid to prevent contamination of the surrounding environment, and provide for safe, easy recovery and disposal of the liquid. Each oil-collection pan 62, 64 is preferably formed integrally with the respective cradle section 12, 14, and typically has a width of twelve inches and a length of two feet. Each pan 62, 64 is provided with an upstanding lip or rim 62′, 64′ for containing the oil. The rest of the cradle unit 60 is substantially identical to the cradle unit 10.

The cradle of the invention adapts readily and inherently to the contour of the underlying support structure or floor, with the spacing between the angle-brackets and between the saddles providing a self-adapting unitary structure, so that uneven or contoured floors will not adversely affect the support provided by the cradle of the invention. Moreover, the inherent resiliency of the material used in the saddles offer shock-absorption characteristics.

While the preferred material for the saddles has been indicated as being polyurethane, other, comparable or equivalent material may be used instead, or composites thereof, as long as these other materials are within the same hardness range of between 50 Shore A and 90 Shore D. Some of these other materials are, for example: nylon; nyrim; polyethylene of all molecular weights (ultra high, high density, medium density, low density, copolymers, homopolymers); rubber such as SBR, EPDM, nitrile, Neoprene (polychloroprene), natural, Hypalon (chlorosulfonated polyethylene rubber), butyl; granulated and rebonded rubber; and recycled plastics; recycled plastic/wood flour or other similarly formulated blends; polypropylene; vinyl (PVC).

While specific dimensions have been given hereinabove, it is to be understood that these have been given only by way of example. The actual dimensions may vary depending upon the lengths and diameters of the coils or rolls intended to be supported.

While the transition regions 20, 22 have been described as having shape or contour described hereinabove, it is to be understood that other methods for producing the shape or contour thereof may employed, as well other different shapes and curvature.

In a variation of the support cradle, the end-cradle section or saddle 12, 14 defines an upwardly-facing concave supporting surface 16, 18 which consists of a first lower or main portion 16′, 18′, respectively, having a first radius R1 of about 18 inches, second upper or tertiary end portions 16″, 18″ each having a second radius R2 of about 36 inches, with the height of each end-cradle section or saddle increasing from a minimum of 1½ inches at the midpoint or center to a maximum of 8½ inches at the extremity or end 24, 26.

Referring now to FIGS. 15-20, there is shown another modification 68 of the cradle unit. This version has especial relevance for the storage of coils, rolls, and the like, on the floor of a truck during transportation thereby, although it is intended for use in all storage environments and locations, whether mobile or fixedly stationary. In order to take into account moments and forces tending to dislodge or displace the support cradles during normal use and loading, there are provided at least one pair of longitudinal rails mounted to the floor of the truck, as shown in FIGS. 18-20. The pair of rails 70, 72 are spaced apart on the floor or other understructure by a distance that accommodates the width of the support cradle unit 68, which width is defined in the direction between the saddles 82 of the cradle unit or alternatively by the length of each connecting brace 90, 92.

In the preferred embodiment, this spacing is either thirty or thirty-six inches, as taken between the outer surfaces 70′, 72′ of the rails. Each rail 70, 72 is provided with a first series of pairs of holes or openings 76, 78 by which screws or bolts permanently affix the rails a floor. There are also provided a second series of equally-spaced apart holes or openings 80 by which support cradles are connected to the rails. The cradle unit 68 is similar to the saddle units of the other embodiments described hereinabove, with the exception of the addition of a pair of spaced-apart metal pins 84, 86 formed in each of the cradle sections or saddles 82. Each metal pin 84, 86 has a projecting or protruding bottom section 84′, 86′ provided in and projecting from the bottom surface 82′ of a saddle 82, which projecting sections 84′, 86′ are received in respective openings of the series of the openings 80 of the rails 70, 72. The openings 80 are of a larger diameter than that of the pins 84, 86 so that the protruding bottom sections 84′, 86′ are loosely received in the holes 80 in order to allow a limited degree of movement. This loose mounting of the pins in the openings 80 is done because, during normal loading of the support cradles with coils, the cradle units experience flexing and bending whereby the distance between the center lines of the pins 84, 86 tend to change, This loose fitting accommodates such flexing and bending. In the preferred embodiment, each metal pin 84, 86 is approximately 4 7/16 inches in length and has a diameter of approximately ⅞ of an inch, with a projecting portion 84′, 86′ that project outwardly from the bottom surface 82′ of approximately 7/16 of an inch. Each metal pin is mounted in a respective saddle by first drilling a hole, and then inserting and adhesively securing a pin in the hole. In the preferred embodiment, the holes 80 of the rail elements have a diameter of approximately 1 1/16 inches, which, given the ⅞ inch diameter of each metal pin 84, 86, allows an approximately 1/16 of an inch play or movement of the pin in a hole, which is more than adequate to allow for the changes in spacing between pins 84 or 86 during flexing and bending under full-load conditions. As mentioned above, the spacing between the two fixed rails 70, 72 is equal to the width of the cradle unit 68.

Also in the preferred embodiment, the length of each rail is approximately 239-⅞ inches a width of three inches, and a thickness of ½ inch. The spacing between holes 80 is approximately five inches, center to center. Also in the preferred embodiment, the spacing between the pins of one saddle and the spacing between the pins of the other saddle are approximately thirty inches, center to center. The width of the cradle unit may be approximately 30 inches or 36 inches, which is equal to length of each of the parallel-arranged steel braces 90, 92. It is, also, noted that in this modification, the parallel-arranged steel braces 90, 92 are not angle-brackets, as in the other embodiments described above, but are just straight elements connecting the pair of saddle supports 82 at portions of the saddle supports above the bottom surfaces 82′ thereof, so that the projecting pins 84, 86 may be used for mounting the cradle unit 68 in the rails 70, 72, in the manner described hereinabove.

Also, in the preferred embodiment, the radius R1 for cradle unit 68 is eighteen inches and the radius R2 is thirty-six inches. The transition region is determined using the same method described hereinabove with reference to the embodiment of FIG. 1.

While the pins 82, 84 have been indicated as being metal, it is to be understood that other, equivalent materials may be used. In addition, the above-listed dimensions have been given only by means of example and are not to be construed to be limiting. Moreover, while the projecting members have been described as pins, other equivalent members may be used instead, it being understood that the projecting members are not to be construed to exclude other equivalent members or manners for mounting the saddles in the holes of the rail elements for a limited degree of movement therein.

While specific embodiments of the invention have been shown and described, it is to be understood that numerous changes and modifications may be made therein without departing from the scope and spirit of the invention as set forth in the appended claims. 

1. A method of supporting a plurality of support cradles used in supporting coils, rolls, and other cylindrical objects, where each support cradle comprises a pair of parallel saddle elements, with each said saddle element comprising a concave upper surface defining a central, lower curved section and a pair of parallel connecting elements each connecting corresponding sections of said pair of saddle elements in order to form a rectilinear-shaped structure, said method comprising: (a) affixing a pair of rail elements to an understructure in a spaced apart manner; (b) loosely attaching a plurality of said support cradles to said rail elements such that each said support cradle is supported by said pair of rail elements; (c) said step (b) comprising inserting projecting members projecting from the bottom surface of said parallel saddle elements into holes formed in said pair rail elements; (d) said step (c) comprising inserting said projecting members into holes such that said projecting members are allowed a limited degree of movement in said holes in order to accommodate distortions induced in said support cradle under load conditions.
 2. The method according to claim 2, wherein each said support cradle has a width approximately equal to the length of a connecting element of a said support cradle, said step (c) comprising mounting the projecting members of one saddle element in holes of one of the rail elements, and mounting the projecting members of the other saddle element in holes of the other of the rail elements.
 3. The method according to claim 1, wherein said step (b) comprises attaching a plurality of support cradles each comprising a concave upper surface upon which rests a portion of a coil or roll, the concave surface defining a central, lower curved section of a radius R1, and a pair of terminal upper curved sections each of a radius R2 greater than R1, and pair of transitional sections, each said transitional section transitioning from said central, lower curved section to a respective one of said pair of terminal upper curved sections; and a pair of parallel connecting elements, each said connecting element connecting corresponding portions of the said pair of saddle elements in order to form a rectilinear-shaped structure;
 4. The method according to claim 1, wherein said step (c) comprises inserting the projecting members into a series of holes equally-spaced along said respective said rail elements, each said hole of said series of holes having a size greater than the size of a said projecting member so that a respective said projecting member is allowed movement therein, in order to accommodate the flexing and bending of a said support cradle under load, whereby said projecting members of a respective said saddle element may be received in a number of different holes of a respective said rail element for allowing different spacing between support cradles.
 5. The method according to claim 3, wherein said step (b) further comprises forming each said transitional section by generating a number of circles of different radii and from a varying center position pt[i] between the center points pt1 and pt2 in a linear relationship using by the equation: pt[i]=pt1+(pt2−pt1)/(r2−r)*abs(r1−r[i]), where pt[i] is a center point of a transitional circle and r[i] is the radius of the transitional circle, connecting the tangents of these generated circles form the curve of each transition region.
 6. The method according to claim 1, wherein said step (c) comprises forming each said saddle element with at least a pair of said projecting members projecting from said bottom surface for mounting in at least a pair of holes of said series of holes of a respective said rail element.
 7. The method according to claim 6, wherein said step of forming comprises forming said holes of series of holes of each said rail element at equally spaced-apart intervals such that said pair of projecting members of a respective said saddle element may be received in a number of different holes of a respective said rail element for allowing different spacing between support cradles. 